When an oil well is first drilled and completed, the fluids (such as crude oil) may be under natural pressure that is sufficient for the well to produce on its own. In other words, the oil rises to the surface without any assistance. In many oil wells, and particularly those in fields that are established and aging, natural pressure has declined to the point where the oil must be artificially lifted to the surface. Subsurface pumps are located in the well below the level of the oil. A string of sucker rods extends from the pump up to the surface to a pump jack device, beam pump unit or other devices. A prime mover, such as a gasoline or diesel engine, an electric motor or a gas engine, on the surface, causes the pump jack to rock back and forth, thereby moving the string of sucker rods up and down inside of the well tubing.
The string of sucker rods operates the subsurface pump. A typical pump has a plunger that is reciprocated inside of a barrel by the sucker rods. The barrel has a standing one way valve, while the plunger has a traveling one way valve, or in some pumps the plunger has a standing one way valve, while the barrel has a traveling one way valve. Reciprocation charges a chamber between the valves with fluid and then lifts the fluid up the tubing towards the surface
In many instances, the well is sandy. A sandy environment causes more wear on a pump and its components as the sand is abrasive. A worn pump does not operate particularly well if at all.
To fix the pump, it is pulled from the well, inspected, and the worn components replaced.
When a tubing pump is repaired, its various components are pulled from the well. For example, pulling the sucker rod string pulls the plunger to the surface. The plunger components can be replaced. Likewise, the standing valve can be pulled and replaced.
The barrel may be worn and require replacement. If the pump is an insert pump, then the barrel can be pulled from the well by the sucker rod string. However, if the pump is a tubing pump, the pump is in-line with, and forms a part of, the tubing. Consequently, the entire string of tubing must be pulled to access and replace the barrel. Pulling the entire tubing string is time consuming and costly. Yet, tubing pumps offer some advantages over insert pumps. For example, tubing pumps provide more fluid capacity that insert pumps.
It is desirable to minimize the cost of repairing and replacing tubing pumps which have barrel damage.